Carbonic anhydrase inhibitors (CAIs) are a group of drugs used to treat glaucoma. They reduce the eye's pressure by reducing the amount of fluid (aqueous humor) produced by the eye. The action of CAIs involves inhibition of an enzyme, carbonic anhydrase. This enzyme is found throughout the body, not only in the eye. Thus CAIs cause side-effects throughout the body in addition to their reducing eye pressure. This study is designed to test these drugs to determine the most effective dose and frequency of administration to reduce intraocular pressure and, at the same time, cause as few side-effects as possible. The study is being performed in four (4) phases to assess the drugs in various doses and in various patient populations.